1. Field of the Invention
The present invention relates to a phase difference delay control system in a distance measuring system in WCDMA (Wideband Code Division Multiple Access) and other cellular phone communication systems and the like. In particular, it relates to a phase difference delay control system that has a transmission line between a reference position and a terminal and that accommodates fluctuation of phase difference occurring in clock crossover units when the distance between the reference position and the terminal including the transmission line is measured.
2. Description of the Related Art
Conventionally, the distance between a reference position and a terminal has been measured at the reference position for the distance measurement by recognizing the distance based upon a difference between the time when a signal is transmitted from the reference position to the terminal and the time when a signal from the terminal in response to the transmitted signal is received at the reference position.
However, when a section of the transmission line between the reference position and the terminal is made longer by using fiber-optic cables, a plurality of transmission channels may be used to transmit the signal and an optimal transmission channel may be selected when the signal is received. In this case, clock crossover units may be needed at both the transmitting and receiving parties in order to match phases of the received signal through the plurality of transmission channels at the receiving party, to create a transmission frame, and to add additional information such as an overhead and the like.
Conventionally, a system that comprises such clock crossover units and measures a distance by transmitting and receiving a signal did not exist.